Brush holder for electric motors



Aug. 15, 1944. w. P. UHLER BRUSH HOLDER FOR ELECTRIC MOTORS 2 Sheets-Sheet 1 Filed May 5, 1942 FIG; 2: I

(Ittomeg Aug. 15, 1944. w P, UHLER 2,356,105

BRUSH HOLDER FOR ELECTRIC MOTORS Filed May 5, 1942 2 Sheets-Sheet 2 -FICiJi 7' "i, r v o Bnnentor Ottomeg Patented Aug. 15, 1944 UNITED STATES PATENT OFFICE BRUSH HOLDER FOR ELECTRIC MOTORS Application May 5, 1942, Serial No. 441,793

Claims.

My invention relates particularly to brush holding means conveniently adaptable to small electric motors such as are usually employed in dental equipment assemblies, but the novel features of construction and arrangement therein embodied may with equal facility be employed in the larger types .of electric motors, and i espeeially directed to means for maintaining the brush in substantially perfect balance on the commutator, whereby sparking may be substantially eliminated.

The principal objects of my invention are to provide a holder for commutator brushes, so constructed and arranged as to facilitate the ready removal and replacement of the brush, and including such an arrangement of the means for urging the brush into contact with the commutator as to insure a perfect balancing of the brush and consequent uniform pressure of said brush on said commutator, whereby sparking and uneven wear on the commutator and brush is substantially obviated.

Other objects of my invention are to provide a brush holder that is so constructed and arranged as to efficiently hold an imperforate commutator brush rigidly in its operative position and to facilitate its convenient removal and replacement.

Further objects of my invention are to provide a spring actuated brush holder which is mounted to move about a suitablyprovided stud, shaft or trunnion, and to provide an adjustable mounting for the captive end of the spring, which is capable of minute adjustment, whereby said spring may urge the commutator brush into engagement with the commutator with varying degrees of pressure as may be found desirable for the best working pressure contact of said brush with said commutator.

My invention comprehends a commutator brush holder having a spring preferably formed of fiat wire, coiled spirally and having its captive end engaged with a sleeve which is mounted on a rotatably adjustable post or stud, and also having its free end pressing centrally with respect to the lateral or transverse length of the brush whereby said brush is urged forwardly with a uniform pressure against the commutator throughout the entire active surface of said brush.

. My invention comprises a brush holder having guides arranged to direct the brush into proper.

position with respect thereto, and includes an imperforate brush which is notched to afford plane surfaces which are arranged to cooperate with said guides and facilitate its ready guidance into position in said holder.

My invention includes a brush holder which is bifurcated to provide Widely spaced bearings rotatably mounted on a rotatably adjustable stud which is provided with a spring mounting sleeve disposed between the bifurcations of said holder and arranged to carry the spring which is designed to urge said brush holder and its brush into contact with the commutator.

My invention also includes all of the various novel features of construction and arrangement as hereinafter more definitely specified.

In the accompanying drawings, Figure 1 is a side elevational view of the driving end bearing cap of an electric motor casing, a portion being shown in section for convenience of illustration, and including a fragment of the armature, its commutator and the cooperative brush holder; Fig. 2 is an inverted plan view of the motor structure illustrated in Fig. 1; Fig. 3 is an enlarged plan view of the brush holder structure per se, a portion being shown in section along theaxial plane of the supporting stud about which the brush holding mounting is rotatably supported; Fig. 4 is an enlarged sectional side elevational view of the brush holder structure illustrated in Fig. 3; and Fig. 5 is a perspective view of the brush which is especially designed to be supported by the brush mounting illustrated in the several figures above described.

In said figures, the bearing cap I of the motor casing, not here shown but which is of well known configuration, provides the bearing boss 2 in which is mounted a bearing 3 for the armature shaft 5 which projects upwardly from said bearing boss 2 and carries the armature 6 having the commutator 9; said armature shaft 5 is conveniently provided with the longitudinally extended groove ID with which a driving pulley may be conveniently engaged.

As shown in Figures 1 and 2, two of the brush holding units such as illustrated in Figs. 3 and 4 are employed and said units are so disposed that the brushes engage the peripheral surface of the commutator on diametrically opposite sides of its axis of rotation. Said brush holding units are secured by the screws l2 with the interposed spacing plates H, to the annular mounting disk l3 which is provided with the diametrically opposite arcuate slots 15 and IB through which the screws I9 and 20 extend to secure said mounting disk I3 to the bearing cap I in rotatably adjusted position.

Referring now more particularly to Figures 3 and i, the brush holding unit comprises the base or frame 22 having the apertures 25 and 26 arranged to receive the screws 12 illustrated in Fig. 2, by which it is attached to the disk l3, and having the extended arm 21 provided with the screw threaded aperture 29 which is arranged to receive the screw 39, see Figs. 1 and 2, to which the lead-in wire 3! may be attached.

Said base or frame 22 is offset forwardly as at 32 and is extended to provide the supporting shelf 35 having the projecting stop lug 36. Said supporting shelf 35 carries the stud 3'1 comprising the intermediate cylindrical enlarged body affording the plane surface arranged to bear with substantial support upon the supporting shelf 35 and having the oppositely directed axial extensions El and 52 of relatively reduced diameters, the extension 51 projecting through a suitably provided aperture 53 in the supporting shelf 35 and through the washer 55 and having the bore 56 to facilitate its expansion, as shown in Fig. 3, by staking, which affords a substantially rigid connection between the stud 3i and its supporting shelf 35 yet permitting a forced rotatable adjustment of said stud with respect to said shelf, which adjustment may be conveniently effected by engaging the apertures 5?" or 58 by a bodkin-like tool and thereby turning said stud 3? with respect to said supporting shelf 35. It may be here noted that the staking action tends to cause such frictional engagement between the washer 55 and shelf 35 and between the flat surface 5?) of the enlarged body and said shelf 35 as to prevent accidental rotation of the stud 3? when thus adjusted by the bodkin-like tool.

The cylindrical extension 52 of said stud 3! serves as a shaft or trunnion on which the brush mounting 59 may be rotatably supported. Said brush mounting 5 is preferably bifurcated to afford relatively spaced bearing lugs Bil and 6| through which the cylindrical extension 52 of the stud 3'! extends. The relative spacing of the bearing lugs 56 and BI tends to prevent undue lateral rocking of the brush mounting and the consequent sparking of the brush as it glides over the commutator.

The outer free end of the brush mounting 59 is formed to provide a brush engaging head 63 having the brush guiding flange 65 and the screw threaded aperture 66 into which the brush retaining screw 8? may be engaged to adjust the brush engaging clip 6:, so that its lip 18 will bear against the brush 72 and rigidly hold it in place in the brush engaging head 63 against the flange y as illustrated in Figs. 1 and 2.

The spring mounting sleeve 15 is disposed on the cylindrical extension 52 of the stud 31 between the bearing lugs 63 and E! of the brush mounting 5S and is secured in rigid relation with said cylindrical extension 52 by the transversely extended pin "15 passing through both the mounting sleeve 15 and the extension 52, as shown in Figs. 3 and 4.

Said spring mounting sleeve '75 is provided with the radially disposed slot Ti, best shown in Fig. l, which extends longitudinally through the periphery thereof and provides a retaining means for the normally bent inner end region 19 of the spirally coiled flat wire spring 93 whose outer end region 91 extends through a suitably provided aperture 92 in the brush mounting 59 and whose extremity 9-3 is bent substantially normal, to overlie the upper surface of the brush mounting 59, so that said spring 90, latched at 76 its inner end region 19 in the slot 11, may urge the brush holder 59 forwardly in the direction of the arrow shown in Fig. 4 whereby the brush held thereby is pressed lightly against the peripheral surface of the commutator 9, as indicated in Figs. 1 and 2.

Referring now to Fig. 5, the brush 12, which is normally of rectangular form, has its forward edge 96 chamfered to conform to the surface of the commutator 9 and has its opposite end region provided with the notch 97 at one corner thereof, which readily permits the withdrawal and replacement of said brush from the brush engaging head 63 without withdrawal of the brush retaining screw 61; more specifically stated, the brush 12 may be conveniently re leased for withdrawal and replacement by only a slight backing off of said brush retaining screw 61. Said notch 91 also forms a rearward restricted unitary projection 99 the notched surface of which serves as a guide cooperative with the screw 6'! to direct it into its proper operative position.

It may be here noted that by slightly rotating the stud 31, tension of the spiral spring can be increased or decreased to provide any desired pressure of the brush 12 on the commutator 9. When thus adjusted to obtain the proper working pressure, the spring 90 may be further adjusted, without disturbing the pressure thus attained, by bending it immediately below the point where it passes through the aperture 92 in the brush mounting 59 in such a manner as to apply stresses in said spring to free the coils thereof from contact with each other, whereby undesirable friction between adjacent coils may be eliminated.

My invention is advantageous in that the length of the brush mounting and the position of bearing are so correlated as to provide the least amount of shift in location of the brush contact with the commutator as the brush wears, whereby it has been made possible to operate the motor through its entire brush life without requiring an adjustment of the position of the brush. Furthermore, the brush is so formed as to not only be readily removed and replaced, but its form facilitates its guiding into proper position in the brush holding head, and the securing of it in such position. Also, the method of attaching the lead-in wires which supply electric current to the brush holder precludes any possibility of stresses being introduced that might disturb the position of the brush on the commutator.

I do not desire to limit my invention to the precise details of construction and arrangement as herein set forth, as it is obvious that various modifications may be made therein without departing from the essential features of my invention as defined in the appended claims.

Having thus described my invention, I claim:

1. A commutator brush holder of the class described, having a frictionally retained support comprising a stud, a brush mounting rotatably engaged with said support, a brush carried by said mounting, and a spring preferably formed of flat spring wire, cooperatively engaged with said stud, spirally coiled and having its free end pressing forwardly in a plane centrally intersecting said brush normal to its transverse width and urging said brush into operative engagement with the commutator.

2. A commutator brush holder of the class de scribed, having a frictionally retained rotatably adjustable support comprising a stud, a brush mounting rotatably supported thereon, a brush carried by said mounting, and a spring, cooperatively engaged with said stud, coiled in a plane which centrally intersects said brush, and means arranged to hold one end of said spring and to cause the free end thereof to urge said brush into balanced contact with the commutator.

3. A commutator brush holder of the class described, having a support comprising a projecting stud mounted for rotatable adjustment, a brush mounting rotatab ly carried by said stud, a brush engaged in said mounting, a spring mounting rigidly engaged on said stud, a, spring spirally coiled in a plane centrally intersecting the bearing surface of said brush and having its captive end engaged in said spring mounting, and its free end tending to urge said, brush into balanced engagement with the commutator.

4. A commutator brush holder of the class described, having a support comprising a stud mounted for rotatable adjustment, a brush mounting carried by said stud and relatively rotatable' thereon, a brush engaged in said mounting, a spring mounting rigidly engaged on said stud, a flat wire spring spirally coiled about itself in a plane centrally intersecting the bearing surface of said brush and having its captive end removably engaged in said spring mounting, and its free end tending to press said brush into balanced engagement with the commutator.

5. A commutator brush holder of the class described, having a support comprising a stud mounted for rotatable adjustment, a brush mounting having relatively spaced bearings rotatably mounted on said stud, a brush engaged in said mounting, a spring mounting rigidly engaged on said stud, a flat wire spring spirally coiled about itself in a, plane centrally intersecting the bearing surface of said brush and having its captive end removably engaged in said spring mounting, and its free end tending to press said brush into balanced engagement with the commutator.

6. A commutator brush holder of the class described, comprising a supporting shaft mounted for forced rotatable adjustment, a brush mounting have relatively spaced bearings mounted for relative rotative movement on said shaft, a brush engaged in said mounting, a spring mounting on said shaft, means arranged to rigidly engage said spring mounting to said shaft so as to move therewith, spring spirally coiled about itself in a plane centrally intersecting the bearing surface of the brush and having its captive end removably engaged with said spring mounting, and its free end tending to iorce said brush into balanced engagement with the commutator.

7. A commutator brush holder of the class described, com arising a supporting shaft mounted for forced rotatable adjustment, a brush mounting have relatively spaced bearings mounted for relative rotative movement on said shaft, a brush engaged in said mounting, a spring mounting having a longitudinally extended slot in its peripheral surface mounted on said shaft, means arranged to rigidly engage said spring mounting to said shaft so as to move therewith, a fiat wire spring spirally coiled about itself in a plane centrally intersecting the bearing surface of the brush and having its captive end removably engaged in the slot in said spring mounting, and its free end tending to force said brush into balanced engagement with the commutator.

8. A commutator brush holder of the class described comprising a base arranged to be secured to a motor casing, a trunnion frictionally engaged in said base and capable of forced relative rotation, a brush mounting having relatively spaced bearings mounted for relative rotative movement on said trunnion and having a forwardly extended arm terminating in a brush receiving head, a brush engaged in said head, a spring mounting disposed on said trunnion between said relatively spaced bearings, a spring spirally coiled in a plane centrally intersecting the bearing surface of said brush and having its supported end engaged with said spring mounting and its free end tending to urge the brush into balanced engagement with the commutator.

9. A commutator brush holder of the class described comprising a suitable supporting trunnion capable of forced rotative adjustment, a brush mounting carried for relative rotation on said trunnion and including a forwardly extending arm terminating in a. brush retaining head having a flange for guiding and positioning a brush, a brush supported in said head, a clip engaging said brush and retaining it in position engaging said flange, and a spring, the tension of which may be varied by the rotation of said trunnion, arranged to press said brush mounting forwardly in a plane centrally intersecting the bearing edge of said brush and tending to urge the brush into balanced engagement with the commutator.

10. A commutator brush holder of the class described comprising a suitably supported trunnion capable of forced rotative adjustment, a brush mounting carried for relative rotation on said trunnion and including a forwardly extending arm terminating in a brush retaining head having a flange for guiding and positioning a brush, a brush engaged in said head and having a forward chamfered edge arranged to engage the commutator and a notch in its opposite edge affording relatively parallel surfaces serving to guide it into position in said head, a clip engaging said brush, and a screw extended through said clip in threaded engagement with said head and cooperative with said flange to direct said brush into proper position in said head.

WILMER P. UI-ILER. 

